LEED analysis of the surface structure of Mo(001)

A detailed comparison between theoretical and experimental LEED data for the Mo(001) surface, using the quantitative r-factor method of Zanazzi and Jona, yields a value for the surface layer contraction of 9.5 ± 2.0%, consistent with the 11.5% found previously by Ignatiev et al. Non-structural parameters are also in agreement, although the surface Debye temperature, 230 K, is slightly higher than found before. r-Factors were used to investigate the effects of all the parameters, and show that an energy-dependent inner potential gives better agreement than a fixed value and that the second layer is contracted by about 1% of the bulk layer spacing. The effect of using different ion core potentials is examined and discussed. A superposition potential which models the surface ion environment is found to have a significant effect on the layer displacement concluded.     

Electronic origin of the surface reconstruction and relaxation of the (001) surface of Mo and W

The reconstruction and the relaxation of the (001) surface of Mo and W are studied by using the tight-binding d band and the Born-Mayer repulsive potential. The d band parameters are set to reproduce band energies of ab initio band calculations at high symmetry points in the Brillouin zone and the parameters in the Born-Mayer potential are chosen to obtain the correct equilibrium lattice constant and the bulk modulus of the bulk crystal. First, we give a detailed discussion on the mechanism of the surface relaxation, and then show that the (001) surfaces of Mo and W are unstable to the c(2 × 2) mode but stable with regard to the (2 × 1) mode. By calculating the energy change up to the fourth order of atomic displacement, we determine the stable surface atomic structure which is in fair agreement with experiments.     

Electronic origin of the surface reconstruction of the (001) surface of Cr,Mo and W

The d-band effects on the reconstruction of the (001) surface of Cr, Mo and W are discussed with a tight-binding model. Response functions corresponding to some models for the reconstruction and their q-dependence are calculated by using Haydrock et al.'s recursion method. The present calculation shows that an energy gain by broadening the surface state peak near the Fermi energy is most remarkable for the model proposed by Debe and King, and therefore gives a theoretical support to it. The energy gain is attributed to an enhancement in the bonding property by pairing of surface atoms in the Debe and King model. Response functions without an electron-phonon matrix element (EPME) are also calculated, which show only a very weak q-dependence. Detailed discussions are given on the mode dependence, that is, on the effect of EPME.     

Electronic structure of K-(001) surface by the density matrix method

The electronic structure of the (001) surface of b.c.c. K has been studied by a direct determination of the density matrix in a local orbital basis. The method is based on a variational treatment of the ground state energy applying the Hohenberg-Kohn-Sham functional formalism. Surface charge density, work function and surface energy are in good agreement with other first principle self consistent calculations.     

Electronic surface resonances and the thermally induced W(001) structure transition

The surface weighted effective potentials of the clean W(001) surface at temperatures T = 550 K[(1×1)] and T = 440 K[(√2×√2)R45°] are experimentally obtained from the surface resonance band structure. It is deduced that the transition W(001)-(1×1) → (√2×√2)R45° is a temperature-dependent reconstruction in which there is a contraction of the top layer atoms towards the bulk involving periodic displacements of the atoms normal to the surface.     

Self-consistent electronic structure for a Mo (001) surface with saturated H adsorption

The band structure for a Mo (001) surface covered with a saturated monolayer of hydrogen is calculated self-consistently using the pseudopotential method in a mixed-basis representation. Two adsorbate bands are found below the bottom of the molybdenum bulk bands. Most of the intrinsic surface states of the clean (001) surface also exist on the hydrogen covered surface at lower energies. The results are used to identify H induced structures observed in recent photoemission studies of hydrogen on W (001).     

Electronic band structure of (001) GaAs-AlAs superlattices

We present the results of a theory of electronic energy bands of superlattices using an application of a recent novel empirical tight binding method. The theory is applied to GaAs-AlAs (001) superlattices with very good agreements with available experimental results for both the direct and indirect energy gaps.     

Relativistic electronic structure of the Pb (001) surface

The surface electronic band structure of the Pb (001) was calculated using the self-consistent, first-principles linear-augmented-plane-wave method and the norm-conserving pseudopotentiai method. In the nonrelativistic case, forbidden gaps appear above and below the Fermi levelin the bulk projected band structure of lead. An occupied surface state at the point and two surface states in a wide forbidden gap above E_F are found. A characteristic feature of the electronic structure of the Pb (001) surface is the absence of a surface state within the forbidden S-P gap in the vicinity of the point. The inclusion of scalar-relativistic effects leads to the merger of several S-P gaps into one wide gap extending throughout the entire Brillouin zone. At the same time, the occupied state at point extends to point and its energy decreases by 2 eV. New, relatively weak surface states in the direction and unoccupied states in the vicinity of the point appear. An unoccupied surface state is found at the bottom of the forbidden gap at point . Including the contribution of the spinorbit pseudopotentiai leads to the appearance of two-spin orbit gas; however, the surface level structure is practically unchanged (except for the disappearance of the unoccupied surface state of P_z-symmetry at point ).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 47–53, October, 1991.     

O2在Mo(001)表面吸附的第一原理研究

采用第一原理方法计算了O2分子在 Mo(001) 表面的吸附,得到了吸附构型的各种参数,并且计算了O2分子在 Mo(001) 表面4个位置（顶位,桥位,穴位垂直,穴位平行）吸附后的能量,结果表明在顶位吸附能最高。通过对O2分子在 Mo(001) 表面吸附的原子轨道电荷分布与态密度图的分析可以看出在吸附过程中主要是O原子的2p轨道电子与钼的4s和4d轨道电子的相互作用。     

O2在Mo(001)表面吸附的第一原理研究

采用第一原理方法计算了O2分子在 Mo(001) 表面的吸附,得到了吸附构型的各种参数,并且计算了O2分子在 Mo(001) 表面4个位置（顶位,桥位,穴位垂直,穴位平行）吸附后的能量,结果表明在顶位吸附能最高。通过对O2分子在 Mo(001) 表面吸附的原子轨道电荷分布与态密度图的分析可以看出在吸附过程中主要是O原子的2p轨道电子与钼的4s和4d轨道电子的相互作用。     

Electronic properties of the single-domain Li/Si(001) surface

Received: 14 October 1996/Accepted: 17 December 1996     

Atomic structure of the (001) surface of CuGaSe2

Hybrid exchange density functional theory is used to study the wide band gap chalcopyrite CuGaSe₂. The formation energies of the experimentally observed (4 × 1) and (1 × 1) atomic scale reconstructions on the CuGaSe₂ (001) surface are calculated for different environmental conditions. The results suggest that a Se-rich (1 × 1) reconstruction, and a Cu-poor, Se-rich (4 × 1) reconstruction, are the only stable surfaces under all the studied environmental conditions. Two complementary mechanisms for the stabilisation of CuGaSe₂ surfaces are proposed, and it is suggested that the presence of Na stabilises the (4 × 1) reconstructions, making them the stable terminations under Na-rich conditions.     

Electronic structure of strained Sin/Gen(001) superlattices

Using the empirical tight binding method we have investigated the electronic properties of the Si_n/Ge_n(001) strained superlattices as a function of the superlattice periodicity and the band misfit. For n ≥ 4 we have found that first and second conduction band states are localized in Si. The hole states localized in Ge appear for n ≥ 4. The difference between the direct and indirect band gaps is reduced from 2.01 eV for bulk Si to 0.01 eV for n=6 which can be considered to be quasi-direct. For the cases n=6 and n=8, the band gap might become direct for large values of band misfit.     

Electronic structure and magnetism of metastable bcc Co(001)

The electronic structure and magnetism of thin films of metastable bcc phase Co(001) consisting of one-, five- and nine-layers is determined by means of all-electron local spin density full potential linearized augmented plane wave (FLAPW) calculations at the lattice constant found for bcc Co stabilized on a GaAs substrate by Prinz. Band structure, surface states, density of states, charge and spin densities and contact hyperfine fields are presented. The center layer of the many-layer films yields a spin magnetic moment of 1.76μ_B which agrees well with results of bulk calculations for bcc Co. The surface layer has a moment (1.94μ_B) which is only 10% greater than the bulk value - in sharp contrast to the enhancement found for other transition metal surfaces [35% for Fe(001), 20% for Ni(001) and over 300% for Cr(001)]. Unlike these other transition metal surfaces, even the first layer below the surface layer in Co has the bulk magnetic moment - which indicates that the spin density, like the charge density, shows very short range screening of the surface-vacuum interface.